This invention relates to a method of treating glaucoma and ocular hypertension in mammals. More particularly, this invention involves a method of lowering intraocular pressure in the mammalian eye by topically applying thereto an ophthalmologically acceptable, effective amount for lowering intraocular pressure of N,N-dimethylaminoethyl carbamate ("N-demethylated carbachol"). The invention further relates to ophthalmic compositions comprising this compound as an active ingredient.
Ocular hypertension is associated with glaucoma, a disease of the eye which is characterized by a progressive increase in intraocular pressure. If the eye is left untreated, such increased pressure will damage the optic nerve head resulting in a corresponding loss of visual field and, ultimately, blindness. Accordingly, a common treatment for glaucoma is the administration to the diseased eye of a substance which is effective in lowering such intraocular pressure.
Basically, there are two types of drugs available for this purpose. One reduces aqueous humor formation and the other increases aqueous humor outflow to reduce the intraocular pressure. Among all of these drugs, pilocarpine, which belongs to the latter type, is the most widely used drug and has been in use for more than a century. Although effective for its intended purpose, when used in the eye pilocarpine and similar drugs produce many unwanted side effects, including local irritation, tearing, burning sensation, ciliary spasm, miosis, and headache. These side effects are thought to be due to two major reasons: (1) instability of the drug at high PH medium necessitating the formulation of pilocarpine-containing ophthalmic solutions at a pH as low as 4.5 to 5.5, and (2) the chemical structure of pilocarpine is entirely different from the natural cholinergic neurotransmitter, acetylcholine, a factor which could produce the sypmtoms of tearing, headache, etc.
It has now been found, according to this invention that intraocular pressure can be reduced in hypertensive eyes without the unwanted side effects commonly associated with pilocarpine and similar drugs.